This invention relates to a gas bag module comprising a gas bag.
Gas bag modules with a so-called ring-shaped gas bag are already known from DE 36 30 685 A1. Here, the front wall is that wall of the gas bag which in the inflated state is directed towards the occupant and which the occupant can impact upon. The middle portion usually is the center of the front wall, which middle portion remains firmly attached to the gas bag module in the case of the known gas bag, so that in the inflated state the above-mentioned ring-shaped chamber is formed.
From DE 199 04 072 A1 there is likewise known a gas bag module with a ring-shaped gas bag, the middle portion of which is prevented from moving towards the occupant by a funnel-shaped part of the module cover. The funnel-shaped module cover is intended to define a deployment direction radially and obliquely outwards, so that occupants disposed clearly outside a central seating position (centrally with respect to the vehicle seat as seen in longitudinal direction of the vehicle) also experience a restraint. Even occupants seated too close to the steering wheel can not be contacted by the accelerated middle portion, which normally first gets in contact with the occupant, as the middle portion is permanently restrained. There is at best allowed a minor movement of the module cover out of the module towards the occupant (deployment direction), this movement being so small that the occupant cannot get in contact with the cover.
In the known gas bags, this middle portion is not available for restraint, not even in the case of heavy occupants, which are disposed in a central seating position and thus hit the front wall in the region of the depression.
The invention provides a gas bag which restrains heavy and centrally seated occupants even more safely. This is achieved in a gas bag module comprising a gas bag which has, with respect to its inflated state, a front wall including a middle portion. The middle portion features a depression in an inflated state of the gas bag, by a restraining means being provided which engages the middle portion and at least partly prevents the same from moving in a direction directed out of the gas bag module. The restraining means is formed such that it is able to release the middle portion after an initial restraint. In the gas bag module proposed, the middle portion is initially restrained, so that the gas bag first of all radially moves radially and obliquely outwards. In this phase of the inflation process, the depression is formed. In the further course of the inflation process, however, the restraining means releases the middle portion, so that the same can move towards the occupant and the occupant can contact the middle portion, and thus can be restrained by the same. This release of the middle portion can be effected obligatorily in any case or depending on specific frame conditions, e.g. from a specific internal gas bag pressure onwards or depending on the position of the occupant. For instance, a heavy occupant or an occupant having an average weight would generate a high internal gas bag pressure in the case of a high impact intensity, when the occupant falls into the gas bag, which high internal gas bag pressure then results in the restraining means releasing the middle portion, and the latter can contribute to a restraint. Via position sensors, the seating position of the occupant can, for instance, be determined. If in the case of an impact the occupant is positioned too close to the gas bag module or off-center, the restraining means would possibly not release the middle portion at all, in order to achieve a better restraining effect and minimize the risk of the occupant being hurt by the air bag.
The restraining means can, for instance, selectively be destroyed or released during deployment, in order to release the middle portion. This destruction can be effected by the high internal pressure or, for instance, also by the influence of temperature due to the hot compressed gas.
In accordance with one embodiment, the restraining means has a limiting strap which is attached to the middle portion. This limiting strap for instance has a tear seam, which is destroyed for releasing the middle portion.
The use of a releasable latching connection as restraining means also is an inexpensive design.
In accordance with another embodiment, the restraining means has a drive for releasing the middle portion. This drive can be actuated by a control, which is coupled to a sensor, depending on the values detected by the sensor.
In accordance with a less expensive embodiment, the restraining means comprises a loop attached to the inside of the middle portion, and a retaining ring in which the loop is suspended. The loop or the retaining ring are destroyed from a specific physical load onwards.